Centrifugally controlled electrical time fuse for a spin stabilized projectile



' y- 1979 L. B. ARONSSON 3,520,254 CENTRIFUGALLY CONTROLLED ELECTRICALTIME FUSE FOR A SPIN STABILIZED PROJECTILE Filed March 26. 1968 arsBgriigro/Lsso 7 US. Cl. 10270.2 2 Claims ABSTRACT OF THE DISCLOSURE Acentrifugally controlled electrical time fuse for a spin stabilizedprojectile. The projectile has an electrical firing circuit including atiming device having an inductance means in an oscillating circuitthereof. A movable tuning means for said inductance means is responsiveto rotational movement of the projectile for varying the frequency ofoscillation of the oscillating circuit. The projectile further has meansfor correlating the energy producing movement of said movable tuningmeans, which results from the application of centrifugal force theretooccurring as the projectile rotates, with the inductance means. Thisprovides frequency variations of the oscillator circuit indicative ofthe cumulative number of revolutions of the projectile.

A time fuze is generally employed in a projectile which is to bedetonated in its trajectory at a predetermined distance from the gun.The time fuze usually includes a clockwork mechanism which actuates theprojectile after the lapse of a predetermined time after the firing ofthe projectile.

It is presumed that the projectile will have a fixed mean velocity v inits trajectory. Based on this assumption a time twill be set in theclockwork mechanism so that the projectile detonates at a distances=v-t.

However, the mean velocity of the projectile will fluctuate owing to theammunition and the gun. The effect of this fluctuation of the meanvelocity will be compensated by a device which will be able to give theproduct v-t a constant value for every predetermined distance. Forinstance, a higher velocity will be compensated by a shorter time insuch a manner that At/t: Av/ v The present invention relates to anelectric device that is provided in a fuze for a projectile that isintended for firing from a gun provided with a rifled barrel, and whichdevice will be able to give the porduct v-t a constant value for everypredetermined distance. The fuze according to the present invention, isprovided with a member that is responsive to centrifugal force. Thismember governs an electric pulse generator in such a way that the pulsefrequency of the generator will be directly proportional to the numberof revolutions of the projectile. The output of the generator isconnected to the input of a preadjustable pulse counter. The output ofthe pulse counter gives a signal when a predetermined number of pulseshave been counted. The output of the pulse counter is connected to ameans for the electric ignition of the projectile.

With a rotating projectile fired from a gun provided with a rifledbarrel, the relation between the number of revolutions and the axialvelocity of the rotating projectile is determined by the screw pitch ofthe terminal rifting at the muzzle of the gun. Consequently, the pulsefrequency f is directly proportional to the velocity v that is f=k-vwhere k is a constant.

The time t for counting n pulses will be t=n/f. But as f=k-v it followsthat i=1z/(k-v) or n=k'v'z. But

United States Patent ice as the distance s=v-t it follows that n=k's.Consequently every pulse interval corresponds to a fixed distanceindependent of the muzzle velocity of the projectile.

The device which determines the pulse frequency of the generator maycomprise a fixed inductance coil provided with an iron or other suitableparamagnetic core that can be displaced or shifted by the centrifugalforce of the projectile. The pulse counter may be a standard type wellknown in this art.

In the drawing,

FIG. 1 is a block diagram of a portion of the electrical circuit in theprojectile, and

FIG. 2 is a diagrammatic representation of a longitudinal portion of theprojectile with portions broken away to show the internal structure.

The pulse generator is indicated at 1 and it consists of a sine waveoscillator and a pulse shaping device of known character. The output ofthe pulse generator is connected to the input of the pulse counterindicated at 2. The output of the pulse counter is connected to theinput of the means indicated at 3 for the electric ignition of theprojectile.

The fuze 4 has a channel 5 perpendicular to the axis 6 of revolution ofthe projectile. In the channel 5 is an iron core 7 that is movable bycentrifugal force during rotation of the projectile and in opposition tothe pressure of the spring 8. When the fuze is not rotating, the ironcore 7 is maintained inside of an immovable inductance coil 9. This coil9 is the coil of the oscillating circuit, which circuit is that of thesine wave oscillator 1. When the fuze 4 begins to rotate, the iron core7 will be moved out of the coil for a certain distance by the action ofcentrifugal force. If the velocity of the projectile increases, both thenumber of revolutions of the projectile and the created centrifugalforce will increase. When the core 7 is drawn further out of the coil 9,the inductance will decrease. When the core 7 is moved further out ofthe coil as above stated and the inductance decreases, the pulsefrequency of the generator will increase and the results heretofore setforth will accordingly follow.

What is claimed is:

1. A projectile comprising an electrical firing circuit including atiming device having an inductance means in an oscillating circuitthereof;

a movable tuning means for said inductance means,

which tuning means is responsive to rotational movement of saidprojectile for varying the frequency of oscillation of said oscillatingcircuit;

means for correlating the energy producing movement of said movabletuning means, resulting from the application of centrifugal forcethereto and occurring with rotation of said projectile, with saidinductance means to provide frequency variations of said oscillatorcircuit indicative of the cumulative number of revolutions of saidprojectile;

whereby a counting of said oscillations may be utilized to providetiming out of a desired delay period for the firing of said projectile.

2. A structure as set forth in claim 1, wherein the movable tuning meansis a paramagnetic mass and wherein said correlating means is a springdisposed to apply a predetermined biasing force to said tuning means.

References Cited UNITED STATES PATENTS 3,006,280 10/1961 Rogers et al10270.2 3,353,486 11/1967 Haiken 10270.2

BENJAMIN A. BORCHELT, Primary Examiner T. H. WEBB, Assistant Examiner

